Mine

class ReverseComparer<T> : IComparer<T>
{
    readonly IComparer<T> defaultComparer = Comparer<T>.Default;

    static IComparer<T> instance = new ReverseComparer<T> ();

    private ReverseComparer()
    {
    }

    public static IComparer<T> Default {
        get {return instance;}
    }

    public int Compare(T x, T y)
    {
        return -1 * defaultComparer.Compare(x, y);
    }
}